The invention relates to additive controllers for supplying or injecting a fluid, usually liquid additives, to large volumes of fluids, also usually liquids. One example is in supplying additive to gasoline.
Prior art additive control and injection devices use positive displacement piston-type pumps to input additives in flow streams.
Problems exist in the positive displacement-type additive devices, in that flows may vary according to velocity, pump pressures and repetition frequencies. Positive displacement-type additive supply systems require reciprocation and other motion in which parts may wear, causing periodic system shutdown for rebuilding and replacement. This is especially true in systems which use high speed reciprocations for positive displacement.
Other problems are addressed by the present invention. One example of a problem with the prior art relates to fluids in gasoline transport lines and tank farm terminals. Each oil company has particular additives to be supplied to gasoline stocks in particular ratios. The additives are added at tank farm terminals by injection into gasoline flowing from pipes into gasoline flowing into tank trucks for regional delivery. Conventional piston-type injectors have been used. Piston-type injectors are difficult to adjust; maintenance related to the positive displacement reciprocations may adversely affect tank farm operation. Injection rates which vary according to viscosity, pump pressure and frequency may create inaccuracies in formulations. Injection rate errors may be cumulative. Broken or breached pistons may increase additive flows in unexpected amounts over long periods without knowledge.
The present invention is directed to solving those problems and other problems of the prior art.